A variety of metal sidings are used in the construction industry to provide the outermost barrier to wind and water on a building's exterior walls. Metal sidings can provide excellent weather resistance and durability and may have a service life of up to years. One common type of metal siding utilizes rather elongated metal panels fabricated from sheet metal, so-called single skin panels. Each panel is typically about a foot to three feet in width. Though they may be cut to any length, they commonly are 30 to 40 feet long and may run as long as 200 feet. The lateral edges of the panels are bent into various lateral patterns to provide side laps. The laps of adjacent panels are overlapped, abutted, interlocked, or in some other fashion connected or “seamed” to form a cover.
Metal panel sidings will incorporate various flashings, trim pieces, sealants, and other components where the field of a wall terminates, such as at the top and bottom of a wall, interior and exterior corners, and around doors and windows. Even where a building has many intersecting walls, doors, windows, and the like, however, the basic assembly of metal panel sidings over the major expanse of walls is fairly uniform. The panels will be mounted on the wall by various clips and fasteners and their laps will be seamed. They perhaps are most commonly installed vertically, that is with the length of the panel running vertically across the wall. The panels, however, may be installed horizontally, that is, with the length of the panel running horizontally across the wall.
Siding systems incorporating single skin panels are commonly classified according to the manner in which they are installed on a wall. In an “exposed fastener” system, panels are configured so that the laps of adjacent panels will overlap. Fasteners, such as gasketed screws, are driven through the overlap and elsewhere on the panels to mount them to the wall. As their name implies, the fasteners are visible to the eye and exposed to the elements. Penetration of water around the fasteners can be a problem, particularly as the siding ages.
“Concealed fastener” systems may incorporate panels which have various prominent rib profiles. That is, the panel is bent along various lateral lines to create ribs running along the length of the panel. The ribs create space underneath the panels which provides clearance for a fastener driven through the overlap between adjacent panels. The panels will overlie the fasteners when the cover is complete, and thus water penetration around the fasteners is less likely.
Other panels are designed to be installed with concealed clips. In a typical concealed clip system, relatively small panel clips are installed on the wall in linear arrays. The arrays may run horizontally across the face of the wall or vertically, but in either event, they define what will become the seam line between adjacent panels. Panels then are installed and seamed on the clips. There are no penetrations through the panels when clips are used. Thus, concealed clip system may be less susceptible to water penetration.
One common type of concealed clip panel is provided with a “hook and cleat” interlock, such as the Wave Panel siding system manufactured by McElroy Metal Mill, Inc. In the Wave Panel system, the lap on one side of a panel is bent over laterally to form a hook running along the length of the panel. The other lap is closely doubled over to form a relatively narrow channel also running the length of the panel. The clips have a similar closely doubled over portion which may be mated with the channel on the panels. An array of clips is engaged with a first panel along its lap channel and mounted to the wall with fasteners. The clips and channel lap on the first panel, thus secured, provide a “cleat” into which the “hook” on the lap of a second panel may be inserted.
It will be appreciated that metal panels are exposed to a range of temperatures, particularly in certain geographic areas. Surface temperature of the panels may be 100° F. higher than ambient air temperature. A steel panel, for example, may expand and contract over a range of 1″ per 100 linear feet. An aluminum panel may expand and contract even more, perhaps over a range of 2″ per 100 linear feet. Panel temperatures will cycle daily and yearly, and over the life of the siding the panels may go through tens of thousands of cycles.
Neither exposed nor concealed fasteners, however, may adequately allow for thermal expansion of the panels. The panels cannot shift relative to the fasteners so changes in temperature can create uneven stress through the panels. Given the extremely high ratio of their length and width to their thickness, differential stress arising from other factors almost always is present in metal panels. Thermal expansion and contraction, however, can exacerbate such stresses and increase waviness and wrinkling of the panels. Such effects are commonly referred to as “oil canning” and reduce, in the eyes of many, the aesthetic appeal of a siding.
Oil canning may be made less conspicuous, and to a certain degree minimized by the design and finish of the panel. Panel ribs not only allow for more even, controlled distribution of stress, but they also break up the surface of the siding, making canning less obvious. Canning also is most apparent when viewed through reflected light. Thus, canning will be less visible when panels are made in lighter colors, or when panels have lower gloss or textured surfaces. Many exposed and concealed fasteners systems rely on such strategies to minimize noticeable canning.
On the other hand, canning is much more apparent in flat, unprofiled panels, or in panels where there are relatively few, more widely spaced ribs. Perhaps because highly profiled panels are so ubiquitous, there is an aesthetic appeal to cleaner, more flush siding finishes. Flatter, less profiled panels also may allow insulation to be installed under the panel without appreciably increasing the overall thickness of the siding. They also may provide an essentially continuous drain plane behind the panel.
Concealed clip fasteners typically will allow for thermal expansion and thereby reduce canning. Hook and cleat style laps and clips, however, cannot be used to provide sidings with a flush finish, that is, a siding where panels are arranged side to side with snug, even seams and “show” sides. Accordingly, manufacturers have developed concealed clip systems where a vertical seam is provided between flush, flat panels. The seams are referred to as “vertical” seams because they extend away from the wall. Depending on the orientation of the panels, “vertical” seams may run horizontally or vertically across the wall.
The PermWall system manufactured by Imetco is an example of a “snap-in” system which joins flat panels at vertical seams. One lap of the panel, together with the clip, serves as a “socket.” The other lap serves as a “post” which may be snapped into the socket. Viewing the panel as oriented for installation, the socket lap of the panels is bent inward and then doubled over. It forms a relatively wide channel extending perpendicularly inward from the panel show side. The post lap extends perpendicularly inward as well, but it is bent into an outwardly facing barb. The clip is essentially a hook on a right-angle bracket. That is, the clip has a flat base with a perpendicular outward extension. The end of the outward extension is provided with an inward facing hook.
A seam may be formed between adjacent panels by first hooking an array of clips over the upper portion of the channel on the socket lap of a first panel. The clip hook extends only partially into the channel. The clips then are mounted to the wall by driving fasteners through their base. The post lap of a second panel then may be snapped into the socket lap of the first panel. That is, the post lap will flex allowing it pass over and beyond the clip hook. Once the second panel is snapped into place, interference between the outward barb on the post lap and the inward facing hook on the clips prevents the seam from disassembling. The panels, however, can “float” on the clips as they expand and contract.
Such panels, like the typical concealed fastener panels, are asymmetrical. That is, the panels do not have a lateral axis of symmetry. More to the point, the laps on asymmetrical panels are different, and typically may be thought of as mating male-female connections. Each panel has a male connection formed in one lap and a female connection formed in its other lap. Thus, installation must proceed in a certain direction across the wall, and removal for repair must proceed in the opposite direction. A damaged interior panel may only be accessed by removing the last panel installed and all other panels “down installation” from the damaged panel. More importantly, the process of removing the down installation panels is highly likely to damage the panels to the extent that they are not suitable for reinstallation.
Moreover, the process of forming asymmetrical panels may increase the susceptibility of the panel to canning. That it, their sides being different, each lap is bent in different ways and to different extents than the lap on the other side of the panel. The stress produced by such forming, like the panels themselves, is asymmetrical. It is not symmetrically distributed through the panel. As the panel attempts to relieve that differential stress, it is more likely to bend and twist.
The PermWall system also cannot easily accommodate panels of differing heights. That is, many architects and property owners may want to create a siding which in large part is flush and smooth. At the same time, by varying the extent to which the show side of panels extend from a wall, i.e., the height of the panels, patterns may be created to accent or enhance architectural features of the structure.
The statements in this section are intended to provide background information related to the invention disclosed and claimed herein. Such information may or may not constitute prior art. It will be appreciated from the foregoing, however, that there remains a need for new and improved systems, apparatus and methods for installing metal panel sidings. Such disadvantages and others inherent in the prior art are addressed by various aspects and embodiments of the subject invention.